Parlor guitars at 24.5 inch/622mm work fine, and I'd guess 600mm with heavy strings could work too.

The two limiting factors are bass response and usable string diameters. You can put a big box on a small neck to achieve bass, though it looks odd, but at some point the low E string for standard tuning has to be so thick that it won't ring out or intonate properly, and if you use a thinner string its tension is too light so again it won't produce the sound you want.

My guess is 600mm is pretty close to the limit - you could check by simply putting the lowest 5 frets in a piece of pine and tensioning a string at your short scale length. You'll feel if is too stiff or too low tension for playability, and hear if it won't intonate properly.

for scale length experiments, you can simply capo at a fret that simulates your preferred length and de-tune to standard pitch. I personally find that de-tuning by a whole tone wakes a lot of guitars up and makes them sound great, so capoing at the second fret, tuning to standard is about the same thing tension-wise, and gives you a 22"-ish scale length. In terms of the box size, the best flat-top I ever played was a O-sized Martin, so that small certainly would work.

It depends somewhat on what they are strung with. As scale lengths get shorter and strings get thicker to compensate they also get "stiffer" which makes the upper partials go "sharp". This creates inharmonicity when combined with the upper partials of other strings. Nylon and gut strings being less stiff to start with suffer less from this than steel strings, so their scale lengths can go a little shorter - 24 inch scale parlor guitars are fairly common. Although I don't think they sound as nice as their long scale cousins, when strung with gut strings they sound O.K. As to body size, I think the length of the body has more effect than the width. Personally I like the "size 1" guitars. The body width is around 12 3/4 inches but the length is still close to the length of an O.M. I have built "strumsticks" with ukulele sized bodies and had them be both loud and reasonably base-y when combined with a 25.4 inch S.L.. If you wish to avoid stress and strain on hands and wrists you might choose less rigorous pieces and concentrate on musicality rather than technique. Many listeners would rather hear a simple piece well played than a masterwork stumbled through. If you are playing for your pleasure you need only satisfy yourself.

This one http://bobgramann.com/deeprun has amazing tone for its size. I think part of the reason for its success is that the waist isn’t pulled in much giving a bit more volume in the body. It is braced very lightly, but stiffly around the bridge so that the whole top pumps. I have made a couple of guitars larger than this braced for extra light strings. They worked very well. If you need easy to play, you could keep the 24.9 scale and build for lighter strings.

I hope that I haven’t violated a rule by linking to my website. I’m traveling and don’t have access to my files any other way. Charlie, if I’ve done wrong, please admonish me and delete the link.

I have made several small guitars with 24" scale (roughly like cutting one fret off a Martin scale guitar). That has been my history in lutherie, I get an idea and build five, six, seven? guitars to try to work it out. When I am satisfied, I never play that guitar again!!!

I have never felt the tone suffered and have some very rich, even bassy, guitars that are about 13.5" at the largest bout. They are not as LOUD, however. My completely unscientific sampling has been that you can certainly have a rich deep sound on a small guitar. But when I tried to play them with other guitars or with a fiddle/banjo/mandolin, I instantly noticed how much quieter they were.

That said, I played an ukulele made by Pepe Romero and that thing was a CANNON. He is very nice, and offered to let me come watch as he voiced one. Stupidly, I've never found the time to take him up on the offer. So there is proof that loud small bodied instrument can be made. Damn if I know how.

I made a steel string once with a 20" scale. It was tricky to play in tune, but sounded OK. It had a normal size body, more or less, that was wedged ('Smith' wedge, not 'Manzer'...). This goes a long way toward making the right arm more comfortable, as does an arm rest bevel.

As you go smaller with the top the balance shifts more toward the treble. You can get a little of that back by making the box deeper, but not as much as you might hope.

The key to keeping your left hand working is to learn to play without bending your wrist. You lose about 25% of your grip strength when you bend your wrist, and that puts more of a load on the muscles and tendons as you play. Using the neck-up 'Classical' position helps a lot.

Great to hear from you! I was just recommending you to my gum surgeon friend-- the best luthier that's underrated.He mentioned something between OO and OOO with rich bass, good mids, and trebles.I said, get a Carruth.

On my end, I don't play guitar all that much...my technique is pretty much self taught after observing classical guitar guys.Maybe I should get some lessons?

On a side note, does anyone have information on the Ditson parlor guitar that Sting uses?I'm tempted to try building something like it...for the office of course.

Matthew, I have built three "parlor" sized guitars basically from the Antes plans (but making the braces lighter and oriented properly LOL) and have been extremely happy with them. They are 24.5 scale length, and while I build them with fairly wide necks that isn't necessary. I string with standard light gauge strings - haven't calculated the tension but it seems reasonable. They don't have the bass of a dread but seem to be well balanced and are incredibly loud. I submitted one for the Acoustic Listening session at last years GAL - a couple of people stopped me afterwards and told me how much they liked it. I asked where they were sitting - they said the very back of the hall.

Back when I was taking voice lessons, my teacher said: "The best way to improve the low end is to work on the high end". 'Good bass' isn't just about power; it's also a function of clarity and separation. For that you need good trebles. A big box that doesn't have clear trebles tends to be 'woofy' and unfocussed.